Fabrication And Optimization Of Organic Photovoltaics Modified By Quantum Dots

The development of renewable energy sources has become the trend of future energy development.As a new type of solar cell,Organic Photovoltaics?OPVs?has the advantages such as abundant materials and low cost,which have attracted increasing attention from researchers.More particularly,it is of great importance to develop OPVs by all solution processing which have the advantages of large-area production.As an electron-transporting material commonly used in the solution processing,zinc oxide?ZnO?is known to have high transparency and significant electron-transporting capabilities,but the incompatibilities between ZnO and the photoactive layer can cause poor interface contact and large series resistance.In addition,there are a large number of defects in ZnO prepared by the sol-gel method,leading to serious charge recombination in inverted OPVs,which limit the further improvement of performances inOPVs.On the other hand,as the most commonly used hole transport material inOPVs,poly3,4-ethylenedioxythiophene/polystyrene sulfonate?PEDOT:PSS?can reduce contact resistance and optimize the energy matching between the electrode and the active layer inOPVs.Nevertheless,one main challenge in the use of PEDOT:PSS is the hygroscopicity,resulting in acid corrosion of ITO substrates,which limits the improvement of efficiency inOPVs.As a result,it is necessary to develop an effective method to modify the interface between hole/electron transport layers and ITO electrodes.It is known that quantum dot?QD?materials can be used as functional layers and interface modification materials for OPVs due to nanoscale effects such as quantum confinement effects.In this work,we have studied two new types of QDs based on graphene-like materials: MoS₂ Quantum Dots?MoS₂ QDs?and Antimonene Quantum Sheets?AM QSs?,to modify ZnO and PEDOT: PSS,respectively.The influences of these two nanomaterials on the interface modification of OPVs finally lead to an effective improvement of OPVs' performance.The main content of the work includes the following two parts:1.MoS₂ QDs were used as interface modification materials for ZnO electron transport layer to achieve high-performance inverted OPVs.A variety of characterization methods were used to systematically analyze the performance of MoS₂ QDs-doped ZnO thin films with different concentrations of MoS₂ QDs,including optical transmittance,surface morphology and chemical composition.The results show that the doped ZnO film has better optical,electrical,morphological,and internal structural properties than the pure ZnO film,while the surface defects of the doped ZnO film are significantly reduced.Subsequently,four kinds of films with different doping concentrations were used as electron transporting layers in inverted OPVs based on P3 HT / PC61 BM,while the effects of different doping concentrations on the performance of OPVs were explored.The results show that the power conversion efficiency?PCE?of the device using ZnO as the electron transport layer is 3.26%,while the PCE of the device modified by MoS₂ QDs reaches 3.83%,with an increase of PCE ?17.5%.2.AM QSs was used as the interface modification material of the PEDOT: PSS hole transport layer inOPVs.Firstly,the systematic investigation of the effects of AM QSs on the properties of PEDOT: PSS thin films demonstrated that AM QSs can optimize the surface morphology of PEDOT: PSS thin films.Subsequently,upsidedownOPVs with ITIC / PDBD-T as the active layer were prepared and the device performance was optimized.The results show that AM QSs can reduce the carrier recombination probability of PEDOT: PSS,increase the hole transport capability of PEDOT: PSS,optimize the energy level matching of the device,and finally achieve an effective improvement of device performance,of which PCE is improved by 8%.